Fig. 3. (a) The golden triangle of solar cell development and (b) comparison of perovskite solar cells and silicon solar cells. Reproduced from ref. 35 with permission from the [Nature Publishing Group], copyright [2018]. (c) The picture of a flexible solar cell and the J–V curves of the best-performing devices under 400 lux under the LED light. Reproduced from ref. 30 with permission from the [Tsinghua University Press], copyright [2018]. (d) Rigid PSCs module. Reproduced from ref. 76 with permission from the [Nature Publishing Group], copyright [2018]. (e) The schematic diagram of perovskite large-area modules. Reproduced from ref. 136 with permission from the [Nature Publishing Group], copyright [2018].