Novel Bio-inspired Halide Perovskite Optoelectronics
Restricted (Penn State Only)
- Author:
- Hou, Yuchen
- Graduate Program:
- Materials Science and Engineering
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- July 21, 2022
- Committee Members:
- John Mauro, Program Head/Chair
Venkatraman Gopalan, Major Field Member
Shashank Priya, Chair & Dissertation Advisor
Noel Giebink, Outside Unit & Field Member
Ismaila Dabo, Major Field Member - Keywords:
- Halide perovskite
Photovoltaic
Optoelectronic system
Biomolecular engineering
Bio-inspiration - Abstract:
- Biological materials and systems have optimized their structure and performance through millions of years of evolution to become sustainable in varying environments while maintaining energetic efficiency. The large library of biomolecules and millions of biological systems provide a database from which specific solutions can be selected to overcome the limitations of artificial materials and devices. The next generation of optoelectronic devices (e.g., photovoltaics or photodetectors) can benefit from the biomolecules or biosystems that have efficient energy conversion capability or light-harvesting features. Hybrid materials such as the halide perovskites can be redesigned with biological materials to not only improve performance but also provide long-term sustainability. Halide perovskite-based solar cells have demonstrated high efficiency of 25.5% as of 2022, approaching the record performance reported for conventional silicon-based photovoltaics. However, halide perovskite photovoltaics have a few grand challenges that need to be resolved for their transition into practical devices. This includes poor environmental stability, low efficiency at the module level, large hysteresis, as well as concerns related to the presence of lead. New design concepts are needed to explore and utilize the multi-functional properties of halide perovskite for the development of novel optoelectronic devices. The incorporation of biomolecules or bio-inspired designs can provide a new direction towards addressing the above-mentioned challenges. Building upon this thought process, this dissertation demonstrates the bio-inspired strategies that show promise in enhancing the performance of halide perovskites. To address the stability issue and efficiency limits of conventional halide perovskite photovoltaics, natural biomolecules with unique functional properties and chemical structures are utilized to engineer the halide perovskite materials to render efficient charge transport, enhanced energy utilization, and strong resistance against environment. Specifically, three types of biomolecules are investigated to be used as additives in halide perovskite solar cells. First, DNA is found to boost the charge transport and extraction within halide perovskite film owing to its charge-conducting nature as well as the formation of close interaction with perovskite grain through a molecular self-assembly process. Owing to the improved charge transport and reduced surface defect concentration, solar cell with improved power conversion efficiency (PCE) from 18.43% to 20.63% are demonstrated. Second, the introduction of Artemisinin in the solvent system induces a unique ‘bi-layer’ perovskite film structure. Owing to the electron-blocking effect induced by the beneficial Schottky barrier formed at the interface between bilayer film and hole transport layer on top, the interfacial photocarrier transfer across the device is improved and recombination loss is minimized. As a result, a high Voc of 1.13 V (vs. 1.06 V for reference device) along with an improved PCE of 20.42 % (vs. 18.28 % for reference device) is demonstrated. Further owing to the hydrophobic nature of the Artemisinin molecule, the top layer in the bilayer film, which consists of Artemisinin-coated halide perovskite nanocrystals, can efficiently block the penetration of moisture into the underneath film thus significantly improving the device stability. The Artemisinin-modified device shows enhanced stability with 95% of initial efficiency of the unencapsulated device well-preserved after one month of ambient exposure. Third, natural lipid molecules with similar structures, Progesterone, and Estrone, were investigated. It is found that Estrone in the halide perovskite precursor solution induces a micro-emulsion feature in the nonionic ink system, which results in a ‘0D/3D bilayer’ structure similar to the case of Artemisinin. A new capping layer composed of 0D nanoparticles of perovskite encapsulated by a hydrophobic lipid membrane, analogous to a cell structure, is formed through a molecular self-assembly process. This 0D layer provides a strong water repellent characteristic, optimum interface microstructure, and excellent homogeneity that drives significant enhancement in device stability. As a result of the beneficial 0D/3D bilayer structure, the PCE and reliability of the solar cell device are simultaneously enhanced with PCE improvement from 19.15% to 21.04%. More importantly, the application of the micro-emulsion ink further improves the film uniformity which enables upscaling of devices from small cells to large-area solar modules. Solar modules with a large active area of 70 cm2 are fabricated using films comprising of 0D/3D bilayer structure. These modules are found to show consistent efficiency of >19% for 2800 hours of continuous illumination in the air (relative humidity of ca. 60%). This emulsion-based self-assembly approach will have a transformative impact on the design and development of stable perovskite-based devices. In addition to photovoltaics, a halide-perovskite-based retina-inspired imaging sensor is also demonstrated. The retina is the essential part of the human visual system that receives light which converts it to neural signals and transmits it to the brain for vision formation. The retina is a highly sophisticated image sensing system with high sensitivity, resolution, and intelligence. The human retina contains cone cells that have signature monochromatic sensitivity to red (R), green (G), and blue (B) light. To realize the artificial version of the color-sensitive cone cells, an intrinsic narrowband photodetector (NB-PD) free of complex color filter array (CFA) is needed. Here a new mechanism is demonstrated to realize the intrinsic narrowband response of halide perovskite-based photodetectors. Through compositional engineering, the halide perovskite exhibits an unbalanced photocarrier transport behavior. Such behavior, coupled with the intrinsic wavelength-dependent optical field distribution and the asymmetric device design, results in spontaneous internal quantum efficiency (IQE) narrowing, which confines the spectral response window of the photodetector within a small wavelength range, i.e., a narrowband response. The successful demonstration of halide perovskite NB-PD with a tunable response window opens the possibility to develop color-sensitive NB-PD arrays for the purpose of full-color imaging. A 32×32 pixels NB-PD array with a response window tuned within red, green, and blue wavelength regime is fabricated based on compositional engineering as well as laser patterning technique. Using a stacking configuration, the RGB monochromatic detection free of CFA and restoration of a 1024-pixel full-color image is successfully demonstrated. A tri-layer neural network algorithm is implemented to mimic the intermediate network of the retinal system in the human eye. This algorithm processes the output signals from RGB sensor arrays and restores the original image with high fidelity. The retina-inspired imaging sensor based on halide perovskite along with the neuromorphic algorithm-assisted image information correction demonstrates a promising device for efficient and intelligent full-color imaging. This will provide an alternative pathway for next-generation imaging technology beyond traditional CMOS or CCD technology.