Interfaces and Hybrid Materials for Photovoltaics

The understanding of physio-chemical processes at the interface between two functional materials has always been a critically important domain for our advancement of optoelectronic technologies. Today this scientific domain has become indispensable to solve the most critical challenges about the sustainable and secure energy supply of the future. In order to accelerate the energy transition, photovoltaics (PV), i.e. the direct conversion of sunlight into electricity, has become a critical and growing component of our energy mix. An approach to overcome the limit of current technologies for further growth is offered by developing solar cells that exhibit a higher power conversion efficiency, i.e. a higher fraction of the absorbed sunlight converted to electricity. Such an increase in efficiency will then lead to an increase in power generation for the same area covered by the solar modules.

In the InHyMat-PV project we turned to a class of emergent solar cell absorber materials that are employed together with silicon (Si) subcells to define a new class of tandem solar cells. Solar cells based on  hybrid organic-inorganic metal halide perovskites (MHP) showed a meteoric rise and nowadays reach power conversion efficiencies that are on par with Si solar cell. With a certified single-junction PCE of 25.7% they also check all boxes to be a perfect tandem partner for other mature technologies, such as Si-based solar cells, but also for all-thin film tandems.

Over the course of the project duration we first, provided comprehensive analysis for the electronic and chemical processes at the interfaces correlated to the device physics in perovskite solar cells. Second, derived novel buffer and interlayer configurations for an implementation of high-performance absorbers into tandem cells guided by advanced characterization routines with variable depth resolution as well as intricate synthesis routes. And, third, we refined the classical methodology needs to capture transient physical and chemical properties of the interface system to generate predictive models for device performance.

In summary, within the InHyMat-PV project we established a new test platform and characterization methodology for interfaces in perovskite solar cells, derived and analyzed new tandem technologies, and build a model for over 30% power conversion efficiency in all thin-film tandems.