| Abstract Scope |
Solar cells have powered calculators for decades, yet their materials and manufacturing methods have evolved significantly. This study compares photovoltaic cells from a 1987 TI-30 SLR+ calculator and a 2025 TI-30X IIS calculator to identify how design choices impact efficiency, cost, and safety. Using light absorption measurements, SEM, XRF, and a Monte Carlo charge-transport simulation, we characterize and model both devices. The older cell uses cadmium telluride (CdTe), while the modern cell uses amorphous silicon (a-Si) in a thinner, lower-cost architecture. Although the modern cell is over twice as efficient in measurements, simulations suggest the CdTe cell likely had higher original performance but has degraded over time. Overall, improvements in manufacturing, materials safety, and cost-effectiveness drive the modern design while maintaining comparable efficiency. |