Bifacial module
A PV module that collects light on both its front and rear faces, using a transparent back sheet or glass to harvest ground-reflected and diffuse light.
Bifacial modules use cells with rear-side contacts that admit light, packaged in glass-glass or transparent-backsheet laminates. The rear side captures light reflected from the ground and diffuse sky light, adding energy without extra land.
The bifaciality factor φ is about 70% for PERC, 75–85% for TOPCon and 85–95% for HJT. Rear irradiance is usually 5–20% of front irradiance, depending mainly on ground albedo, module height above ground, row spacing and rear shading from racking.
- Energy gain over monofacial: typically 5–10% on grass or soil, 10–15% over light gravel or sand, and 20% or more over snow or white membranes (NREL and Sandia field studies).
- Gains are largest on single-axis trackers with one module in portrait and high mounting.
- Rooftop installations close to the roof gain little.
Bifacial glass-glass modules dominate new utility-scale projects; vertical east-west bifacial arrays are used in agrivoltaics and produce morning and evening peaks.
Related terms
All terms →- Albedo
The fraction of incoming solar radiation that a surface reflects, from 0 (absorbs everything) to 1 (reflects everything).
- Solar tracker
A motorised mounting structure that rotates PV modules or mirrors to follow the sun, raising the irradiance they receive over the day.
- TOPCon
Tunnel Oxide Passivated Contact: an n-type silicon cell whose rear uses an ultra-thin oxide and doped polysilicon layer to extract current with minimal recombination.
- Heterojunction (HJT) solar cell
A cell that sandwiches an n-type crystalline silicon wafer between ultra-thin amorphous silicon layers, giving very high voltage and a low temperature coefficient.
- Agrivoltaics
The combined use of the same land for solar power generation and agriculture, such as crops or grazing beneath or between PV arrays.
- DHI (Diffuse Horizontal Irradiance)
Solar radiation reaching a horizontal surface after being scattered by molecules, aerosols and clouds, excluding the direct beam from the sun disc.