fi ber-shaped, [ 8 ] wearable, [ 9 ] and even semitransparent [ 10,11 ] perovskite solar cells.In particular, semitransparent solar cells are of great interest for future applications, such as power-generating window panels in buildings or automobiles, which would raise the usage ratio of solar energy without occupying additional space. [ 12,13 ] For example, building-integrated solar cells could lead to the creation of completely self-sustaining, pollution-free buildings. Furthermore, semitransparent solar cells can be stacked in a tandem device architecture in which a cell with a higher bandgap is placed atop another with a lower bandgap. [14][15][16] To date, most demonstrated semitransparent solar cells have been based on high-bandgap absorbers, thin polymers, and amorphous silicon absorbers, which result in critical losses in overall effi ciency. Perovskitebased absorbers possess outstanding lightabsorbing characteristics, and the explicit tradeoff between PCE and transparency can be adjusted by varying the thickness of the absorbing layer. In this strategy, the conventional approach is to form perovskite layers thin enough to attain the desirable high transparency. [17][18][19][20][21][22][23] Uniform, thin perovskite fi lms have been produced via evaporation or gasassisted spin-coating techniques. Roldán-Carmona et al. fabricated semitransparent perovskite solar cells by employing an evaporated 280 nm thick perovskite absorber layer, achieving a PCE of 7.73% and an average visible transmittance (AVT) of 19%. [ 10 ] Additionally, centimeter-scale, 135 nm thick evaporated CH 3 NH 3 PbI 3 thin fi lms were reported to have PCEs of 9.9%. [ 18 ] Using a gas-assisted spin-coating process, continuous 107 nm thick CH 3 NH 3 PbI 3 thin fi lms were demonstrated with PCEs of 8.1% and AVTs of 19%. [ 24 ] Along with the development of thin perovskite absorber layers, strategies for enhancing the carrier collection effi ciency, including the use of Ag nanowire electrodes, [ 20 ] graphene electrodes, [ 17 ] and atomically thin ZnO cathode buffer layers and Al 2 O 3 capping layers, [ 21 ] have been suggested to compensate for the limited light absorption.Despite the success of these approaches, the practical fabrication of large-scale continuous, thin perovskite fi lms remains challenging, and issues preventing commercial viability, including reproducibility and stability, are unresolved. Obtaining a highly effi cient, moderately thick absorber layer with a restricted open aperture is a prerequisite for achieving practical semitransparent photovoltaic devices. Two suggested Semitransparent solar cells have attracted signifi cant attention for practical applications, such as windows in buildings and automobiles. Here, semitransparent, highly effi cient, 1D nanostructured perovskite solar cells are demonstrated employing anodized aluminum oxide (AAO) as a scaffold layer. The parallel nanopillars in the perovskite layer enable construction of hazefree semitransparent devices without any hysteresis behavior. By controlling the...
