Researchers have unveiled an innovative approach to enhancing solar energy conversion by exploring a new class of materials known as alkali mono-pnictides. Led by Yu Kumagai, this study published in PRX Energy, which translates to “Physical Review X Energy,” investigates the potential of replacing selenium (Se) in solar cells with Group 15 pnictogens like phosphorus (P), arsenic (As), and antimony (Sb). This shift aims to improve upon the relatively low power conversion efficiency of traditional selenium-based solar cells, which has plateaued at a maximum of 6.5% over the past 140 years.
The study highlights sodium phosphide (NaP) as a particularly promising candidate. NaP is composed of earth-abundant elements, making it not only a sustainable choice but also potentially cost-effective. According to the researchers, NaP exhibits a “slightly indirect band gap” and a high optical absorption coefficient just above the absorption onset, which are critical characteristics for effective solar energy absorption. Additionally, it features light electron and hole effective masses, and ambipolar dopability, which are advantageous for optimizing charge carrier mobility in solar cells.
However, the research does not shy away from addressing challenges. The team found that phosphorus (P) vacancies could hinder the photovoltaic performance of NaP. To mitigate this, they propose strategies for chemical potential control to reduce these vacancies, thereby enhancing the material’s overall efficiency.
The preliminary results from the growth of NaP powder samples are promising, revealing a direct band gap of 1.66 eV, which closely aligns with the predicted value of 1.62 eV. This suggests that NaP could be a viable alternative to existing materials in the solar energy market, potentially leading to more efficient solar cells that harness sunlight more effectively.
The implications of this research extend beyond laboratory findings. If successfully developed and commercialized, these new photovoltaic materials could significantly lower the cost of solar energy production and contribute to a more sustainable energy future. The transition to using abundant materials like NaP may also attract investment in solar technology, spurring innovation and expanding market opportunities within the energy sector.
As the world continues to seek cleaner energy solutions, the findings from Kumagai and his team represent a significant step forward in the quest for more efficient and accessible solar power technologies, as detailed in their recent publication in PRX Energy.
