Although the power conversion efficiency of perovskite solar cells has increased from 3.81% to 22.1% in just 7 years, they still suffer from stability issues, as they degrade upon exposure to moisture, UV light, heat, and bias voltage. We herein examined the degradation of perovskite solar cells in the presence of UV light alone. The cells were exposed to 365 nm UV light for over 1,000 h under inert gas at <0.5 ppm humidity without encapsulation. 1-sun illumination after UV degradation resulted in recovery of the fill factor and power conversion efficiency. Furthermore, during exposure to consecutive UV light, the diminished short circuit current density (Jsc) and EQE continuously restored. 1-sun light soaking induced recovery is considered to be caused by resolving of stacked charges and defect state neutralization. The Jsc and EQE bounce-back phenomenon is attributed to the beneficial effects of PbI2 which is generated by the decomposition of perovskite material.

Perovskite solar cells have great potential for high efficiency generation but are subject to the impact of external environmental conditions such as humidity, UV and sun light, temperature, and electric fields. The long-term stability of perovskite solar cells is an important issue for their commercialization. Various studies on the stability of perovskite solar cells are currently being performed; however, the stability related to electric fields is rarely discussed. Here the electrical stability of perovskite solar cells is studied. Ion migration is confirmed using the temperature-dependent dark current decay. Changes in the power conversion efficiency according to the amount of the external bias are measured in the dark, and a significant drop is observed only at an applied voltage greater than 0.8 V. We demonstrate that perovskite solar cells are stable under an electric field up to the operating voltage.

Organic-inorganic hybrid perovskite solar cells (PSCs) have been extensively studied because of their outstanding performance: a power conversion efficiency exceeding 22% has been achieved. The most commonly used PSCs consist of CH3NH3PbI3 (MAPbI3) with a hole-selective contact, such as 2,2′,7,7′-tetrakis(N,N-di-p-methoxyphenylamine)-9,9-spiro-bifluorene (spiro-OMeTAD), for collecting holes. From the perspective of long-term operation of solar cells, the cell performance and constituent layers (MAPbI3, spiro-OMeTAD, etc.) may be influenced by external conditions like temperature, light, etc. Herein, we report the effects of temperature on spiro-OMeTAD and the interface between MAPbI3 and spiro-OMeTAD in a solar cell. It was confirmed that, at high temperatures (85 °C), I− and CH3NH3 + (MA+) diffused into the spiro-OMeTAD layer in the form of CH3NH3I (MAI). The diffused I− ions prevented oxidation of spiro-OMeTAD, thereby degrading the electrical properties of spiro-OMeTAD. Since ion diffusion can occur during outdoor operation, the structural design of PSCs must be considered to achieve long-term stability.

1% at 0.4798 cm 2 , and 14.0% at 1.045 cm 2 , respectively, while the corresponding module efficiencies are 25.1% at 866.45 cm 2 , 24.4% at 13 177 cm 2 , 19.2% at 841 cm 2 , 19.0% at 23 573 cm 2 , and 12.3% at 14.322 cm 2 , respectively. [2-4] Silicon modules account for over 90% of the solar cell market share. [5] Although thin-film solar modules compete with silicon solar cells, the efficiency of the former is lower by ≈5 percentage points (%p). [2-4] Recently, a perovskite solar cell was reported, which used an organic metalhalide hybrid material with an ABX 3 perovskite crystal structure as the lightabsorbing layer. [6-8] This type of perovskite solar cell has attracted much attention as a next-generation solar cell. Kojima et al. first reported a perovskite solar cell with an efficiency of 3.8% in 2009. [9] Initially, perovskite solar cells did not receive much attention because of their poor stability and efficiency. However, research has increased since Park and co-workers reported an efficiency exceeding 9% with stability over 500 h in ambient conditions. [10,11] In the last six years, the efficiency of perovskite solar cells increased from 14.1% to 25.2%, which is the thirdhighest single-junction efficiency reported thus far. [2-4] However, perovskite solar cells are facing commercialization issues. For their successful application to the industry, the following problems must first be addressed: [12,13]-Upscaling (high-efficiency, large-area module demonstration)-Stability (performance degradation over times)-Toxicity (lead (Pb) and cesium (Cs) issues). Stability and toxicity problems were introduced relatively early in the literature. [10,11] Immense efforts were devoted to finding the origin of and solution to the degradation of perovskite solar cells. Owing to the dedicated efforts of countless researchers, the degradation factors were identified as the humidity, light, [14,15] heat, [16,17] and electric fields. [12,18] Degradation issues have been addressed with the development of stable perovskite compositions, electron-transfer layers (ETLs) and hole-transfer layers (HTLs), and encapsulations. Several groups have reported perovskite solar cells that passed the International Electrotechnical Commission (IEC) stability test, while Grätzel and co-workers reported a cell that remained stable for one year. [19-22] Thus, stability has been significantly improved. The status and problems of upscaling research on perovskite solar cells, which must be addressed for commercialization efforts to be successful, are investigated. An 804 cm 2 perovskite solar module has been reported with 17.9% efficiency, which is significantly lower than the champion perovskite solar cell efficiency of 25.2% reported for a 0.09 cm 2 aperture area. For the realization of upscaling high-quality perovskite solar cells, the upscaling and development history of conventional silicon, copper indium gallium sulfur/ selenide and CdTe solar cells, which are already commercialized with modules of sizes up to ≈25 000 cm 2 , are reviewed. ...

Copper has attracted significant interests as an abundant and low‐cost alternative material for flexible transparent conducting electrodes (FTCEs). However, Cu‐based FTCEs still present unsolved technical issues, such as their inferior light transmittance and oxidation durability compared to conventional indium tin oxide (ITO) and silver metal electrodes. This study reports a novel technique for fabricating highly efficient FTCEs composed of a copper ultrathin film sandwiched between zinc oxides, with enhanced transparency and antioxidation performances. A completely continuous and smooth copper ultrathin film is fabricated by a simple room‐temperature reactive sputtering process involving controlled nitrogen doping (<1%) due to a dramatic improvement in the wettability of copper on zinc oxide surfaces. The electrode based on the nitrogen‐doped copper film exhibits an optimized average transmittance of 84% over a spectral range of 380 −1000 nm and a sheet resistance lower than 20 Ω sq−1, with no electrical degradation after exposure to strong oxidation conditions for 760 h. Remarkably, a flexible organic solar cell based on the present Cu‐based FTCE achieves a power conversion efficiency of 7.1%, clearly exceeding that (6.6%) of solar cells utilizing the conventional ITO film, and this excellent performance is maintained even in almost completely bent configurations.