Ambient processing of organometal halide perovskites for wearable photodetector devices

Organometal halide perovskites have recently attracted plenty of attention in solar cell applications due to their high charge-carrier mobilities, high photoconversion efficiencies and ease of fabrication. Herein, we demonstrate the broadband characteristics of CH3NH3PbI3-xClx thin film photodetectors that were fabricated using ambient processing conditions. Two different photodetector devices were designed and fabricated. The first device (architecture 1) involves spinning a thin perovskite film between the top and bottom electrodes, while the second (architecture 2) includes additional electron and hole transport layers between the contacts. The achieved responsivity was 2 A/W at 2 V for architecture 1 compared to 0.42 A/W at -2 V for architecture 2. We have observed that the perovskite film formed on top of the PEDOT: PSS layer is non-uniform with large crystalline domains. In some parts, the crystal domains were as large as 1.76 μm, whereas better surface coverage was achieved on top of the ITO, which had smaller crystal domains (1.4 μm). This resulted in the dark current of architecture 1 being one order of magnitude higher in comparison to architecture 2. This new fabrication method allows for low-cost optoelectronic device fabrication in uncontrolled laboratories. Contrary to recommendations in the literature, our findings show that simple fabrication with the PEDOT:PSS layer enables good photoconduction properties in room temperature conditions.