The synthesis of solution-processed two-dimensional (2D) layered organohalide (CH3(CH2)3NH3)2(CH3NH3)n-1PbnI3n+1 (n = 2, 3, and 4) perovskites is presented, where inkjet printing was used to fabricate heterostructure flexible photodetector (PD) devices on polyimide (PI) substrates. Inks for the n = 4 formulation were developed to inkjet-print PD devices that were photoresponsive to broadband incoming radiation in the visible regime, where the peak photoresponsivity R was calculated to be ∼0.17 A/W, which is higher compared to prior reports, while the detectivity D was measured to be ∼3.7 × 1012 Jones at a low light intensity F ≈ 0.6 mW/cm2. The ON/OFF ratio was also high (∼2.3 × 103), while the response time τ on the rising and falling edges was measured to be τrise ≈ 24 ms and τfall ≈ 65 ms, respectively. Our strain-dependent measurements, conducted here for the first time for inkjet-printed perovskite PDs, revealed that the Ip decreased by only ∼27% with bending (radius of curvature of ∼0.262 cm-1). This work demonstrates the tremendous potential of the inkjet-printed, composition-tunable, organohalide 2D perovskite heterostructures for high-performance PDs, where the techniques are readily translatable toward flexible solar cell platforms as well.
Keywords: flexible photodetector; inkjet printing; organohalide 2D perovskites; photoluminescence spectroscopy; strain dependency.