Traditional high-performance photodetectors rely on materials like silicon and InGaAs, but their manufacturing is costly and structurally complex. While low-cost perovskite-based photodetectors present an excellent alternative capable of self-powered operation for low-power IoT devices, broadband variants cannot differentiate targeted wavelengths, and existing narrowband variants require impractical high driving voltages. Alternative strategies that use optical filtering techniques or materials with ultrawide bandgap often fall short due to limited detection range and complicated fabrication routes that are impractical for commercial, large-scale production.
In a new paper published in Light: Advanced Manufacturing, a team of scientists, led by Assoc. Professor Pongsakorn Kanjanaboos from Advanced Technologies for Energy and Sustainability Lab, School of Materials Science and Innovation, Faculty of Science, Mahidol University, Thailand, and co-workers have developed a new strategy for energy-selective broadband photocurrent amplification in self-powered mode. The main objective of their study was to combine two perovskite materials with different bandgaps to generate more current and increase the overall current flow by absorbing the targeted wavelength region. CsPbBr3, a high-bandgap material, can absorb high-energy wavelengths shorter than 540 nm and transfer this energy to the triple-cation perovskite which can harvest more photon energy from both direct absorption and perovskite-perovskite energy transfer. They designed a photodiode-based perovskite photodetector with a chocolate-chip-cookie-like hybrid structure in which wide bandgap CsPbBr3 perovskite micro-droplets (chips) are embedded into a slot-die coated triple-cation perovskite matrix (cookie) by using spray coating technique. The nature of the spray coating, along with the careful annealing strategy, provided homogeneous and discrete microdroplets that spread throughout the base layer. These microdroplets redistribute the light propagation due to refractive index contrast and concentrating optical energy at the chip/cookie interfaces. With different band energy values, energy-funneling pathways are created to allow efficient charge transfer from chips to cookie matrix. This mechanism enhances the photocarrier generation and collection with ~7.9% under green light (532 nm) and ~8.5% under ultraviolet light (365 nm) compared to reference photodetector device. Interestingly, although a trade-off between specific detectivity and spectral responsivity was observed owing to more interfaces, fast photoresponse at such wavelengths within a range of tens to hundreds of microseconds and linear dynamic response (LDR) of >100 dB sufficiently fast enough and reliable for many practical optoelectronic sensing applications.
"Unlike conventional PD optimisation strategies that aim to minimise dark current and maximise detectivity for overall device performance improvement, the novelty of the chocolate-chip-cookie structure is the introduction of enhanced optical interaction within the absorber layer to enhance photocarrier generation at targeted wavelengths via an optical-scattering-induced electric-field redistribution and carrier-funnelling mechanism." they added.
"The proposed chocolate-chip-cookie-like hybrid structure is beneficial for self-powered photodetection applications, including UV monitoring sensors, environmental IoTs devices, and low-power imaging systems. The use of slot-die and spray coatings also demonstrates the compatibility of our proposed chocolate chip-cookie-like hybrid structure with scalable and cost-effective solution-processing techniques for large-scale photodetector manufacturing." the scientists predict.
