Inkjet-Printed Organohalide 2D Layered Perovskites for High-Speed Photodetectors on Flexible Polyimide Substrates

The synthesis of solution-processed two-dimensional (2D) layered organohalide (CH₃(CH₂)₃NH₃)₂(CH₃NH₃)_n-1Pb_nI_3n+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 τ_rise ≈ 24 ms and τ_fall ≈ 65 ms, respectively. Our strain-dependent measurements, conducted here for the first time for inkjet-printed perovskite PDs, revealed that the I_p 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.