The solar cell technology is experiencing tremendous growth globally, as well as the building integrated photovoltaics (BIPV) field [1-4]. The latter is growing extremely fast because the integration of photovoltaics (PV) into building roofs and façades provides cost-effective energy solutions, as modules can substitute building envelopes, such as roofing or glass windows. Windows make up a large percentage of modern building real estate, therefore transforming them into PV devices they would drastically increase the available area for on-site electricity generation.

However, the adoption of this technology depends on its ability to transmit light in terms of average visual transmittance (AVT) coupled with a reasonably high photo-conversion efficiency (PCE) [1-4].

Currently, most commercially available devices consist of patterned crystalline silicon (c-Si) wafer technology [1]. Although Si-based PV offers both high PCE and AVT, it results in an unpleasant and impeded view. On the other hand, amorphous silicon (a-Si) can enable a homogeneous appearance for semi-transparent photovoltaic (STPV) by decreasing the thickness of the light-absorbing material such that semi-transparency is achieved. However, the latter result in windows with an inherent low color rendering index (CRI).

Perovskite PV technology has taken giant steps from fundamental science to device engineering, achieving up to 26% photo-conversion efficiency [5-7] in almost a decade time. The possibility to exploit this technology on glass substrates gives an unbeatable power to weight ratio in comparison to similar photovoltaic systems, thus opening new possibilities and new integration concepts in BIPV.

Also, perovskite solar cells (PSCs) hold an advantage over traditional silicon solar cells in the simplicity of their manufacturing processing [6-7]. While silicon cells require expensive, multi-step processes, at high temperature and under high vacuum in cleanroom facilities, PSC materials can be realized in lab environment using a variety of inexpensive, simpler, and low-temperature solution processing and deposition techniques with the potential to be scaled up for large-area device fabrication [7].

Moreover, there is an enormous effort to push PSC from research and development at the lab-scale level to a  large-scale industrial level, making PSC an outstanding contender for STPV. So far, top-performing STPV using thin perovskites have reached 12.6% PCE with 21.5% AVT, and 2.7% LUE [6].

Here, we developed a STPV technology with a relatively high AVT (43%), PCE (6%), LUE (3%), and CRI (89%) based on laser patterning of thin-film PSC. Our design philosophy is based on micro-striped solar cells separated by a fully transparent gap, providing high transparency. The device architecture is a thin-film, planar, n-i-p configuration with a commercial transparent conductive oxide-coated glass bottom contact electrode, an inorganic electron-transport layer, a hybrid halide perovskite absorbing layer, an organic hole-transport layer, and a thermally evaporated or sputtered top contact electrode. The material layers are fabricated by inexpensive solution processing methods and deposited onto substrates at low temperature by scalable and rapid printing techniques, such as spincoating.

Furthermore, all developments target material-efficient and sustainable fabrication approaches for technology transfer to industry.