Bidirectional Voltage Regulation for Integrated Photovoltachromic Device Based on P3HT‐Electrochromic Unit and Perovskite/Organic Tandem Solar Cells

Integrated electrochromic devices powered by photovoltaic cells have evoked a lot of interest due to their promising commercial prospects. However, their application has been restricted by the voltage adaption between the self‐powered voltage and the color‐changing threshold voltage (Vt). Herein, a strategy of bidirectional voltage regulating is proposed to develop a novel stand‐alone integrated photovoltachromic device (I‐PVCD), which integrates perovskite/organic tandem solar cells (P/O‐TSCs) to drive color‐changing process of conjugated poly(3‐hexylthiophene) (P3HT) films. To lower the driving‐voltage of electrochromic layer, C60 is introduced to decrease the onset oxidation potential of P3HT film, and thus leading to a reduced Vt of 0.70 V benefiting from the enhanced highest occupied molecular orbital level and decreased charge transfer resistance from 67.46 to 49.89 Ω. Simultaneously, PBDB‐T is utilized as the hole transport layer in the interconnecting layer of CsPbI2Br/PTB7‐Th:IEICO‐4F P/O‐TSC to improve its open‐circuit voltage (Voc) to 1.85 V. Under their synergetic merits, a I‐PVCD with a wider self‐adaptive voltage range is achieved. This device can undergo fast and reversible chromic transition from beautiful magenta to transparent only under the solar radiation, and demonstrates a coloration efficiency of 351.90 cm2 C−1 and a switching time of 2 s besides its excellent operating reliability. Integrating electrochromic units with photovoltaic cells presents a promising prospect in modern energy self‐sufficient and aesthetically more appealing devices. This work proposes a strategy of bidirectional voltage regulation to develop the stand‐alone photovoltachromic devices via the synergetic effects of C60 with outstanding charge storage ability and PBDB‐T with passivation function on solar cells.