What is the efficiency limit of a single-junction silicon solar cell?

Efficiency limit of solar cells with index-near-zero photon management layers

The maximum power conversion efficiency of a solar cell as defined by the Shockley-Queisser (SQ) radiative recombination limit relies on the assumption that the collection probability for all photogenerated electron/hole pairs is unity. This assumption implies a virtually infinite mobility ${\ensuremath{\mu}}_{\mathrm{n}}$ of the photogenerated charge carriers. In order to compute the radiative efficiency limit with finite mobilities, we solve the continuity equation for minority carrier transport including an additional photon recycling term that accounts for emission of photons by radiative recombination and their subsequent reabsorption. This approach quantitatively connects the SQ approach with the classical diode theory. Even when assuming radiative recombination as the only loss mechanism, the maximum efficiency achievable within our model is reduced drastically when ${\ensuremath{\mu}}_{\mathrm{n}}$ drops below a critical value. This critical value depends on the absorption coefficient, the doping density of the absorber material, as well as on the thickness and the light trapping scheme of the solar cell. Thus, these material and device parameters gain a fundamental importance as soon as finite carrier mobility is considered. Our theory yields a criterion that has to be fulfilled by any photovoltaic material in order to guarantee charge separation even in an otherwise most ideal case. Exemplary application of our model to three real photovoltaic materials, crystalline silicon $(c\text{\ensuremath{-}}\mathrm{Si})$, amorphous silicon $(a\text{\ensuremath{-}}\mathrm{Si}:\mathrm{H})$, as well as $\mathrm{Cu}(\mathrm{In},\mathrm{Ga}){\mathrm{Se}}_{2}$ (CIGS), shows that mobilities of $c\text{\ensuremath{-}}\mathrm{Si}$ and CIGS are three, respectively, 1 order of magnitude above this critical limit whereas the effective hole mobilities in $a\text{\ensuremath{-}}\mathrm{Si}:\mathrm{H}$ are scattered around the critical value. A comparison between solar cells and light-emitting diodes with finite mobility and finite nonradiative lifetime reveals that materials for these complementary devices have to fulfill different requirements.

Successfully designing an ideal solar cell requires an understanding of the fundamental physics of photoexcited hot carriers (HCs) and the underlying mechanism of unique photovoltaic performance. Harnessing photoexcited HCs offers the potential to exceed the thermodynamic limit of power conversion efficiency, although major loss channels employing ultrafast thermalization of HCs severely restrict their utilization in conventional bulk-absorber-based solar cells. Spatially confined semiconductors, especially 2D van der Waals (vdW) materials, offer several advantages, such as strong Coulomb interaction, high exciton binding energy, strong carrier–carrier scattering and weak carrier–phonon coupling, resulting in slow HC cooling and restricted loss channels. This Review provides a detailed mechanistic understanding of the HC cooling dynamics in confined vdW layered materials for efficiently utilizing HCs and discusses the role of carrier multiplication in designing a solar cell with the power conversion efficiency exceeding the Shockley–Queisser limit. Additionally, we analyse the major energy loss channels that limit the efficiency of a conventional solar cell, as well as the promises held by the 2D vdW heterostructures for an efficient HC solar cell. Furthermore, we highlight the challenges and opportunities involved in successfully utilizing HCs in practical solar cells with efficiencies beyond the thermodynamic limit. Conventional solar cells suffer from the thermalization energy loss of hot carriers, which sets the Shockley–Queisser limit. This Review highlights the insightful mechanisms of slow hot carrier cooling dynamics and efficient carrier transport/extraction in 2D van der Waals heterojunctions, following opportunities in practical hot carrier solar cells.

Potential application of multilayer n-type tungsten diselenide (WSe2) sheet as transparent conducting electrode in silicon heterojunction solar cell

Conventional single junction solar cells are fundamentally limited by the Shockley–Queisser efficiency limit, while hot carrier solar cell (HCSC) aims to overcome this through efficient hot carrier extraction, thereby revitalizing the application prospects of wide bandgap materials in photovoltaic technologies. This study demonstrates that isonicotinamide (IA)—previously shown to enhance bulk perovskite solar cells via defect passivation—can be strategically applied to quantum dots (QDs) by replacing oleylamine (OLA) ligands. Systematic studies reveal a non-monotonic dependence of the thermalization coefficient (Qth) on IA/OLA ratios in CsPbIxBr3−x QDs. At optimal concentrations, Qth decreases to 1.89 ± 0.059 mW⋅K−1⋅cm−2, accompanied by a prolonged carrier lifetime (17.7 ns), attributed to dual functional groups of IA passivating undercoordinated Pb defects. However, excess IA overcrowds surfaces of QDs, displacing OLA and creating new defects that increase Qth. These competing effects determine an optimal IA/OLA ratio for Qth minimization, which is almost two orders of magnitude lower than in bulk materials. The suppressed hot carrier thermalization could significantly enhance the maximum achievable power conversion efficiency of HCSC. This work establishes the perovskite QDs as promising wide bandgap absorbers for HCSC and provides a ligand-engineering strategy to optimize hot carrier dynamics.

High-efficiency rectennas for radio frequency (RF) energy harvesting have been studied for decades, but most of the literature straightforwardly applies the rectenna aiming at dedicated RF sources to this situation, even though the level of input power is significantly different. Since previous studies address antenna design collecting more ambient RF power, the improvement of power conversion efficiency (PCE) has emerged in a scattered way, because the theoretical limit of PCE has not yet been characterized, and the optimal rectenna structure approaching such maximum PCE is still uninvestigated. In this paper, we characterize the performance limit of rectennas with input power ranging from -20 to 0 dBm, proposing optimal rectenna design demonstrating the maximum PCE. The maximum achievable PCE is cast into a mathematical programming problem. Solving this optimization model clarifies the effect of design factors, including operational frequencies, rectifier topologies, and parameterization. To achieve the maximum PCE, our investigation shows that the optimal rectenna structure should not only optimize those design factors but also eliminate the matching circuit between an antenna and a rectifier for ultralow-power scenarios. The resultant PCE at 2.45 GHz is 61.4% and 31.8% at -5 and -15 dBm, respectively, closely approaching the theoretical bound.

Multi-junction solar cells are vital in developing reliable, green, sustainable solar cells. Consequently, the computational optimization of solar cell architecture has the potential to profoundly expedite the process of discovering high-efficiency solar cells. Copper indium gallium selenide (CIGS)-based solar cells exhibit substantial performance compared to those utilizing cadmium sulfide (CdS). Likewise, CIGS-based devices are more efficient according to their device performance, environmentally benign nature, and thus, reduced cost. Therefore, the paper introduces an optimization process of three-layered n-CdS/p-CIGS/p-GaAs (NPP)) solar cell architecture based on thickness and carrier charge density. An in-depth investigation of the numerical analysis for homojunction PPN-junction with the ’GaAs’ layer structure along with n-ZnO front contact was simulated using the Solar Cells Capacitance Simulator (SCAPS-1D) software. Subsequently, various computational optimization techniques for evaluating the effect of the thickness and the carrier density on the performance of the PPN layer on solar cell architecture were examined. The electronic characteristics by adding the GaAs layer on the top of the conventional (PN) junction further led to optimized values of the power conversion efficiency (PCE), open-circuit voltage (VOC), fill factor (FF), and short-circuit current density (JSC) of the solar cell. Lastly, the paper concludes by highlighting the most promising results of our study, showcasing the impact of adding the GaAs layer. Hence, using the optimized values from the analysis, thickness of 5 (μm) and carrier density of 1×1020 (1/cm) resulted in the maximum PCE, VOC, FF, and JSC of 45.7%, 1.16 V, 89.52%, and 43.88 (mA/m2), respectively, for the proposed solar cell architecture. The outcomes of the study aim to pave the path for highly efficient, optimized, and robust multi-junction solar cells.

9 - New Directions for Organic Thin-Film Solar Cells: Stability and Performance

Crystalline silicon solar cells have long dominated the global photovoltaic market due to their mature manufacturing processes, excellent stability, and abundant raw material reserves, accounting for over 90% of the total PV market share. However, single-junction c-Si solar cells are approaching the Shockley-Queisser (SQ) efficiency limit of ~29.4%, creating an urgent need for next-generation PV technologies to achieve higher power conversion efficiency (PCE). Monolithic perovskite/silicon tandem solar cells (PSTSCs) stand as the most commercially promising technology to surpass the single-junction efficiency limit. Since their first demonstration in 2015, PSTSCs have experienced rapid technological advancement, with the certified PCE reaching 35.0% in 2026. This review posits that their rapid efficiency ascent is not serendipitous but driven by synergistic innovations across critical subsystems. We systematically deconstruct these efficiency drivers, encompassing top-cell materials, bottom-cell architecture, and optical management. We conclude by outlining future research frontiers essential for transforming this lab-champion technology into a mainstream energy solution.

Tin Sulfide (SnS) is a promising absorber material for solar energy harvesting owing to the high absorption coefficient. Here, a novel inverted planar heterostructure of SnS based solar cell (ITO/NiOX/SnS/ZnO/Al) has been proposed for better efficiency among the different electron transport layers (ETLs), PCBM, C60, CeOX, and ZnO. The performance of the SnS based solar cell was theoretically studied by the Solar Cell Capacitance Simulator (SCAPS) software. Initially, we have been observed the device performance with different ETL materials to find the better ETL material. The layer parameters of the HTL, absorber layer, and ETLs have been optimized to find out the best performance of the device. The device showed efficiencies of around 26.44%, 26.33%, and 26.38% with the ETLs PCBM, C60, and CeOX respectively. The maximum power conversion efficiency (PCE) of ∼28.15% has been observed after incorporating ZnO ETL in the designed architecture of the SnS-based solar cell. Then, we have been investigated the performance of the SnS-based solar cell with ZnO ETL for the various value of carrier concentration, thickness, and bulk defect of the SnS absorber layer, defect of the interfaces of NiOX/SnS and SnS/ZnO, back metal contact’s work function, and its operating temperature. The variation of the different parameters has exhibited a substantial effect on the device performance. The VOC, JSC, FF, and PCE of the optimized SnS-based solar cell with ZnO ETL showed 0.8954 V, 37.316452 mA cm−2, 84.24%, and 28.15%, respectively. The visualization of the results indicates that ZnO might be a potential ETL for the highly efficient, low-cost inverted planar solar cells based on SnS.

Solution-processed tandem solar cells, that stack two or more single junction subcells with different band gaps to harvest photons in the full solar spectrum more efficiently, have attracted increasing attention recently. Organic photovoltaics and perovskite solar cells are promising candidates for the top and/or middle subcells of tandem solar cells because the solar cells are able to capture visible and near-infrared photon energy. However, there are few materials to choose from for the infrared bottom subcell. While PbS and PbSe colloidal quantum dots (CQDs) have been gaining much attention for short-wave infrared solar cells owing to their wide-range bandgap tunability and solution process compatibility. Among various CQD-based solar cells, PbS / ZnO depleted heterojunction solar cells showed a power conversion efficiency (PCE) over 13% in 2020 (Nat. Commun. 2020, 11 , 103). But there is a limited number of literatures reporting PbS-QD-based solar cells working in the low photon energy region (< 1.0 eV) where optical absorption of PbS QDs is weak. Thus, we have focused on PbS QD/ZnO nanowire (NW) structures with the aim of achieving efficient carrier transport and light absorption simultaneously (J. Phys. Chem. Lett. 2013, 4, 2455). We then investigated the performance of PbS QD/ZnO NW solar cells using PbS CQDs with the first exciton absorption peak locating in the short-wave infrared region. (ACS Energy Lett. 2017, 2, 2110). Here, we develop high efficiency infrared PbS CQDs solar cells aimed at the bottom subcell of tandem solar cells, and discuss the potential for the bottom subcell.We constructed two different solar cells using infrared PbS QDs with the first exciton absorption peak at 1550 nm, which is nanowire-type solar cell (NW-cell) and planar-type solar cell(P-cell). The ZnO nanoparticles layer (P-cell) or ZnO nanowire (NW-cell) as an electron acceptor formed on highly infrared transparent 1% Ta-doped SnO2 (TTO) conductive glass substrates. PbS CQD were deposited on the ZnO layers from a PbS QD octane solution via a layer-by-layer dip coating method. The PbS-QD layer were treated with a tetrabutylammonium iodide (TBAI) methanol solution to replace the insulating oleic acid ligands with iodide anions (PbS-I). The external quantum efficiency (EQE) spectra and the structures of the P-cell and NW-cell are shown in the figure. In the almost entire wavelength region ranging from 380 to 1700 nm, the EQE gave higher in the NW-cell than in the P-cell. The best performing planar-type solar cell exhibited a PCE of 2.68% (Jsc= 18.9 mA/cm2; Voc=0.316 V; FF=0.451) under 100 mW/cm2 simulated AM 1.5G illumination. On the other hand, ZnO nanowire-type solar cells gave a PCE of 5.38% (Jsc=38.7 mA/cm2; Voc=0.335 V; FF=0.415), and showed almost twice as high Jsc value (38.7 mA/cm2) as that of the planar-type solar cells. The integrated Jsc of the nanowire-type solar cells obtained from the EQE spectrum 38.5 mA/cm2 is approximately the measured Jsc value. To investigate the potential for the bottom subcell of the tandem solar cell, infrared-performance of nanowire-type solar cells were studied using different short-cut filters. The solar cells exhibited 2.50 % PCE (Jsc=19.2 mA/cm2; Voc=0.307 V; FF=0.424) and 1.11% PCE (Jsc=8.6 mA/cm2; Voc=0.282 V; FF=0.460) under a long-pass filtered one-sun illumination (l >810 nm (perovskite solar cells equivalent), and l>1100 nm (Si solar cells equivalent)), respectively. All these results indicate that the ZnO nanowire PbS QD solar cells are promising candidates to construct tandem devices with perovskite and c-Si solar cells. Figure 1

A conductive adhesive ink for carbon-laminated perovskite solar cells with enhanced stability and high efficiency

The solar light radiation causes some of the heat to be trapped inside the solar cell that raises the solar cell’s temperature, then reduces the electrical efficiency of the overall system. The thermal radiation from solar light causes overheating on the solar cell surface and degrades its functionality. In this study, the thermal insulation coating has been proposed to prevent interior trapped heat. Different nanocoating systems have been developed using nano-Titanium Dioxide (TiO2) namely T1B2 and T2B2, nano-Zinc Oxide (ZnO) namely Z1B2 and Z2B2 and nano-Tin Oxide (SnO) namely S1B2 and S2B2. All the nanoparticles have been synthesized at various weight percentages which are 20wt.% and 60wt.% in the B2 binder system, Methyltrimethoxysilane (MTMS) / nitric acid (HNO3). The incorporation of nanoparticles increases the hydrophobicity of binder coating in which the Water Contact Angle (WCA) of coating improves up to 105°. The embedded nanoparticles increase the surface roughness, then reduce the contact of water to the substrate’s surface. Apart from that, the coating is also capable to halt the drastic increment in surface temperature. The result has shown that the B2 binder coating increases the surface temperature of solar cell by 2.54°C after 1hr of Xe 1000 W/m2 irradiation. The raise in temperature is due to the strong oxidation of nitric acid. However, the incorporation of nano-ZnO and nano-SnO in B2 binder matrix capable to reduce the temperature of the solar cell. The wide bandgap of both nanoparticles induces good stability of coating at high operating temperature. The Z1B2 and S2B2 has reduced the temperature of solar cell by 7°C and 3°C, indicating their great thermal insulation property for solar cell application.

Carrier Dynamics Engineering for High-Performance Electron-Transport-Layer-free Perovskite Photovoltaics

This study aims to prepare nano-polymer materials that contribute to improving the electrical properties and improving the properties and efficiency of solar cells. Also, the prepared materials are inexpensive compared to solar cells prepared from inorganic materials such as silicon and germanium. This study deals with the effect of a polymer layer containing pure polymer of 3-Hexylthiophene and Thiophenein combination with silver nanoparticles on the electrical properties relevant to solar cell applications. The polymer of 3-Hexylthiophene and Thiophene was prepared individually, then a polymer composite (3-Hexylthiophene-co-Thiophene) was made. after that then a Core-Shell of (3-hexylthiophene - CO-Thiophene) @ Ag Nanoparticles was made, after which two-layer and three-layer solar cells were made from the prepared samples. The polymers were manufactured using the additive polymerization method using chloroform (CHCl3) solvent and were subsequently characterized. The research focused on the electrical properties of the pure polymer (P3HT@Thio) doped with silver nanoparticles and its efficiency, with special attention to its application in solar cells. We found the best results in the two-layer structure. Current-voltage (I-V) measurements were conducted under illumination at room temperature with varying incident light intensities over a small area. Key parameters such as electrical conductivity, activation energy, open-circuit voltage (Voc), short-circuit current density (Jsc), maximum power point parameters (JP, VP), fill factor (FF), and power conversion efficiency (η) were calculated for all samples under standard laboratory conditions. The results demonstrate that the highest electrical conductivity (2.39x10⁻³ s.cm⁻¹) was achieved with the polymer blend of 70% P3HT-CO-30% PTH doped with 25% silver nanoparticles (Ag NPs). The activation energy, ranging from 0.1448 eV to 0.8537 eV, showed the lowest value at the same polymer blend, likely due to the proximity of the conduction and valence band levels induced by nanoparticle doping. Additionally, the efficiency of the solar cells was assessed, revealing significant improvements in device performance. The optimal efficiency, measured at 10.488%, was observed in the (PEDOT)/ (PCPM+Active Layer) structure. All relevant parameters, including Jsc, Voc, FF, and power conversion efficiency (PCE).