Diversifying Progress in Solar

Influence of Charge Transport Layers on Capacitance Measured in Halide Perovskite Solar Cells

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

Sputtered transparent electrodes for optoelectronic devices: Induced damage and mitigation strategies

A low band gap quinolizino acridine based molecule was designed and synthesized as new hole transporting material for organic-inorganic hybrid lead halide perovskite solar cells. The functionalized quinolizino acridine compound showed an effective hole mobility in the same range of the state-of-the-art spiro-MeOTAD and an appropriate oxidation potential of 5.23 eV vs the vacuum level. The device based on this new hole transporting material achieved high power conversion efficiency of 12.8% under the illumination of 98.8 mW cm(-2), which was better than the well-known spiro-MeOTAD under the same conditions. Moreover, this molecule could work alone without any additives, thus making it to be a promising candidate for solid-state photovoltaic application.

Self-Seeding Growth for Perovskite Solar Cells with Enhanced Stability

Photovoltaic research explores and expands solar cell development, with efforts focusing on improved performance output, applying more cost-efficient and environmentally friendly materials, and establishing longer-lasting durability. Moreover, photovoltaic research also investigates solar cell degradation and understanding degradation mechanisms to develop solutions for better preserving cell performance. Perovskite solar cells possess strong technological potential due to their industrially feasible processing procedures and competitive performance output. However, perovskite solar cells face difficulties with industrial and commercial scalability alongside intrinsic instability during operation. This work addresses the processing behind perovskite solar cell development, encompassing procedures that develop a cell's architecture. Furthermore, characterization techniques involve efficiency, fill factor, short-circuit current density, and open-circuit voltage parameter outputs, capacitance over area readings, and how the absorption mechanism collects charges from incoming photons. Standardized performance analysis with perovskite solar cells will then pivot into degradational experimentation and analysis. As this work reviews degrading solar cell performance, degradation mechanisms and their effects will be discussed and further explored. Conclusions will address specific degradation phenomena occurring within the cells as supported by characterization analysis. Furthermore, future work targets additional plausible characterizations for pursuing degradation analysis and discusses refining experimental procedures for a more critical approach in analyzing solar cell stability.

Within the past several decades, photovoltaic technology is an emerging pioneer in the renewable energy field. Driven by the rapid decline in the price of photovoltaic products, the cost of photovoltaic power generation is becoming cheaper or even lower than the cost of thermal power generation. Among various photovoltaic technologies, organic-inorganic hybrid perovskite thin film solar cells are promising candidates for the next generation of solar cells in consideration of their outstanding advantages such as low-cost, easy manufacturing processing and high power conversion efficiencies. Perovskite solar cells stem from dye-sensitized solar cells. Within less than a decade of rigorous research and development in perovskite solar cells, the efficiency is boosted up to 25.2%. Aforementioned high PCE is mainly attributed to outstanding photovoltaic properties such as the long diffusion length of carriers, high optical absorption coefficient, excellent carrier mobility, etc. Meanwhile, the main barriers of commercialization for the perovskite solar cells are the poor stability of the devices, and the possible environmental pollution caused by lead. Herein, we briefly reviewed the opportunities and the challenges of this game changer in photovoltaic field. The development prospective are also discussed.

Very recently, lead-halide perovskites have received much attention as a promising class of low-cost and high-performance photovoltaics materials since the first report of all-solid-state perovskite solar cells (SCs) in 2012 [1]. Organic-inorganic hybrid CH3NH3PbI3 is a model material of metal-halide perovskites, and its optical and electronic properties have been insensitively studied. It is known that perovskite CH3NH3PbI3 has excellent optoelectronic properties for SC applications: large optical absorption coefficients, extremely low densities of traps and defects, and long diffusion lengths of carriers. Because the energy conversion efficiencies of SCs depend on the luminescence quantum efficiency of the target semiconductor material [2,3], photoluminescence (PL) spectroscopy is one of the most powerful techniques for characterizing and developing new materials and structures for SC devices. By taking advantage of high-efficiency PL of lead-halide perovskites, we can directly monitor their carrier generation, recombination, and transport dynamics of SCs using time-resolved PL spectroscopy [4]. Here, we summarize the optical properties of solution-processed CH3NH3PbI3 and CH3NH3PbBr3thin films and single crystals and discuss the physical origin of high conversion efficiencies in perovskite SCs. Optical studies on high-quality thin films and single crystals are required for a deep understanding of the intrinsic optoelectronic properties of lead-halide perovskites. We studied photocarrier dynamics of high-quality CH3NH3PbI3 and CH3NH3PbBr3thin films and single crystals using one-photon excited PL (1PL) and two-photon excited PL (2PL) spectroscopy [5-7]. In thick single crystals, the photocarriers are generated at the near-surface region under one-photon excitation and in the interior region under two-photon excitation. The time-integrated 1PL peak energy is higher than the 2PL peak energy. The 1PL peak energy shifts to lower energy with delay time after laser excitation. The 1PL lifetime is shorter than the 2PL lifetime. These dynamical PL behaviors of thick single crystals are different from those of thin films. In thin films, the photocarriers are created homogeneously throughout the sample thickness under one- and two-photon excitation [8]. The spatial distribution of photocarriers determines the PL spectrum and dynamics: The PL dynamics of thick single crystals can be explained by fast carrier diffusion and photon recycling (photon emission and reabsorption) [5-7]. In SC device structures, the perovskite CH3NH3PbI3 layer is sandwiched between the mesoporous TiO2electron-transport layer and the spiro-OMeTAD hole-transport layer. Charge carrier dynamics in the perovskite solar cells were studied by means of PL and photocurrent (PC) imaging spectroscopy. Simultaneous PL and PC imaging measurements revealed a positive correlation between the PL intensity and PL lifetime, and a negative correlation between PL and PC intensities [8]. These correlations are a result of the competition between the escape of photocarriers from the perovskite layer and the recombination of photocarriers within the perovskite layer. Moreover, from the excitation-fluence dependence of the PL decay curves in thin films and SCs, we conclude that the carrier injection at the interface determines the device performance of perovskite SC [9,10]. Our systematic PL studies provide an essential information for developing high-performance devices based on metal-halide perovskites. Part of this work was supported by JST-CREST (Grant No. JPMJCR16N3). References M.M. Lee et al, Science 338, 643 (2012). O. D. Miller et al., IEEE J. Photovoltaics 2, 303 (2012). L. Zhu et al., Opt. Express 24, A740 (2016). Y. Kanemitsu, J. Mater. Chem. C 5, 3427 (2017). Y. Yamada et al., J. Am. Chem. Soc. 137, 10456 (2015). T. Yamada et al., Adv. Electron. Mater. 2, 1500290 (2016). T. Yamada et al., Phys. Rev. Applied. 7, 014001 (2017). Y. Yamada et al., J. Am. Chem. Soc. 136, 11610 (2014). D. Yamashita et al., J. Phys. Chem. Lett. 7, 3186 (2016). T. Handa et al., J. Phys. Chem. Lett. 8, 954 (2017). D. M. Tex et al., Phys. Rev. Applied 7, 014019 (2017).

Perovskite solar cell (PVSC), after its invention since 2009, has attracted tremendous attention from both academia and industry, because of its low cost, ease of manufacturing features and the sky-rocketing efficiencies being achieved within such a short period of time. Currently, the new efficiency record has reached 21.0%, comparable to that of the commercialized PV technologies developed for decades, such as multi-crystalline Si, CIGS and CdTe thin film solar cells. It is very possible that PVSCs would one day step over the threshold of marketization, share or even overturn the current PV market dominated by crystalline-Si solar cells. However, there are still several obstacles to be overcome on the road towards PVSC industrialization. This paper has reviewed the brief developing history and the current research status of PVSCs, and explained: Why PVSCs are so important in the next-generation solar cells, why organometal halide perovskites work so well as light absorbers, and what the inherent differences are among different cell configurations. The prospects on how to realize scale-up industrialization of PVSCs have also been given in the sequence of efficiency, stability, cost, toxicity, and short-term objectives. Resolutions to the remaining challenges according to their orders of technical difficulty and importance have also been discussed.

Perovskite (PVK) solar cells (PSCs) have garnered considerable research interest owing to their cost-effectiveness and high efficiency. A systematic annual review of the research on PSCs is essential for gaining a comprehensive understanding of the current research trends. Herein, systematic analysis of the research papers on PSCs reporting key findings in 2023 was conducted. Based on the results, the papers were categorized into six classifications, including regular n–i–p PSCs, inverted p–i–n PSCs, PVK-based tandem solar cells, PVK solar modules, device stability, and lead toxicity and green solvents. Subsequently, a detailed overview and summary of the annual research advancements within each classification were presented. Overall, this review serves as a valuable resource for guiding future research endeavors in the field of PSCs.

Progress in tailoring perovskite based solar cells through compositional engineering: Materials properties, photovoltaic performance and critical issues

Perovskite solar cell (PSC) can be regarded as a continuation of dye sensitized solar cell (DSSC) in terms of the sensitization phenomena that occurred in the functioning molecules. In 2012, a breakthrough propose has been made for the sensitization of PSCs, in which a solid-state structure is offered as an equivalent sensitizer used in DSSC. The power conversion efficiency (PCE) of those solid-state cells reached about twofold of its initial value during the past several years. Immediately after, the researchers followed this propose worldwide. They have introduced an improved efficiency of as much as 20%, which was originally started from its initial value of 4%, just in 4 years. Thus, the new concept, solid perovskite molecules, has eliminated the need for the liquid electrolyte in DSSC while still carrying the advantages of organic solar cells (OSCs). Therefore, the distinctive material of PSC--the organometallic halide molecules (also known as OMH or organic-inorganic trihalides)--inclined an unexpected reputation for solar cell (SC) researches. Hence, it seems that we will witness a new age for solar conversion devices depending on the recent hopeful progresses on PSCs. The high rate of photovoltaic (PV) conversion capacity in PSC is generally expressed by the basic properties possessed by the organic-inorganic perovskite crystal, such as better optical properties and well diffused charges along huge distances during the charge transport. In addition, a low temperature processing is applicable during its production. Moreover, the perovskite layer provides a tunable band gap. Therefore, depending on better developments on designed molecules, PSC may gain extreme performances compared to the other competitors, such as OSC or DSSC devices. This chapter starts with a general discussion on the need for an affordable clean energy conversion device that is urgent for the future of humanity, due to publicly well-known global warming issue. In Section 2, basic properties of PSC are mentioned together with their structure and working principles. Section 3 continues with an overview on organometallic perovskite molecules after a brief introductory history is presented. The absorption and band gap properties are also discussed. Since most perovskite materials need a hole transporting material (HTMs) within the PSC, the kinds of HTMs that are designed for PSCs are described in Section 3. The rendering of long-term stabilization has special importance for PSCs since the instability issue remained idle in spite of those recent increased efficiency values attained by various research groups. Therefore, the stability issues are discussed in a separate part in Section 4. We finally close the chapter discussing the challenges and opportunities relying on the chapter content. We note that the recent investigations on PSCs have special importance for its large-scale realization in order to make them ready for the photovoltaic industry of the future. Hence, there are various announced meetings focusing on its mass production due to the unexpected sharp rise of the perovskite efficiency in the last 6 years. Hence, all the new cutting-edge scientific findings are also dealt with commercialization issues now, in order to attain the desired low cost fabrication, including the yield of high purity and the formation of smooth films during the continual manufacture of perovskite layers.

Efficient MA-free Pb-Sn alloyed low-bandgap perovskite solar cells via surface passivation

High-efficiency solar cells with low manufacturing costs have been recently accomplished utilizing different technologies. III-V-based tandem solar cells have exhibited performance enhancement with a recent efficiency of greater than 39% under AM1.5G and 47% under concentration. Integration of such III-V materials on a relatively cheap Silicon (Si) substrate is a potential pathway to fabricate high-efficient low-cost tandem solar cells. Besides, perovskite solar cells, as third-generation thin film photovoltaics (PV), have been meteorically developed at a reasonable cost. At present, there are still questions for cost reduction of perovskite materials and solar cell modules because of their limited commercialization. In this review, stacking Si solar cells with III-V material to form Si-based III-V tandem solar cells is presented with different integration technological routes. Also, perovskite/Si tandem solar cells have been reviewed alongside their main engineering challenges introduced through the fabrication of perovskite-based tandem solar cells. Finally, a comparison between III-V tandem solar cells, Si-based III-V tandem solar cells, and perovskite-based tandem solar cells is introduced so that the best technology for a specific application could be determined. The review provides a comprehensive study of two different technologies (III/V and Perovskite) to demonstrate the most valuable cost reduction availability for each.

Solution-processed Ruddlesden-Popper (RP) interlayers in lead halide perovskite solar cells (PSCs) present processing challenges due to fast film formation and uncontrolled growth of phases and layer thickness at interfaces. In this work, an alternative, solvent-free, thermal co-evaporation process is developed to deposit RP interlayers. The method provides precise control on interlayer thickness and enables understanding its role on charge-carrier extraction. Studying RP film growth reveals the development of heterointerfaces when deposited on three-dimensional (3D) perovskite layers. This allows a large thickness window with an optimum between 20 nm and 40 nm to improve the optoelectronic properties of the underlying 3D perovskite. Solar cells using evaporated interlayers achieve power conversion efficiency of 21.6%, compared to 19.6% for untreated devices, driven by improvements in the open-circuit voltage and fill factor. This work sheds light on the importance of phase and thickness control of passivation layers, which ultimately determine the solar cell performance in state-of-the-art PSCs.