This invention relates to the field of photovoltaic technology, disclosing a photovoltaic backsheet, its preparation method, and a photovoltaic module. The photovoltaic backsheet sequentially comprises a weather-resistant outer layer, a
barrier layer, and a functional inner layer. The functional inner layer includes an acidic substance adsorption and
neutralization layer (located between the
barrier layer and a
humidity buffer layer) and a
humidity buffer layer (whose upper surface contacts the lower encapsulation film of the photovoltaic module). The acidic substance adsorption and
neutralization layer comprises a matrix (low-acid-value
acrylic resin with an
acid value ≤ 5 mg KOH / g) and alkaline nanoparticles dispersed in the matrix. The
humidity buffer layer comprises a main resin and a controllable
moisture-absorbing material dispersed in the main resin. The thickness ratio of the humidity buffer layer to the acidic substance
neutralization layer is 1.5-2:1. Through the synergistic effect of each layer, this photovoltaic backsheet, by passively blocking
moisture, actively adsorbing and neutralizing
corrosion sources, and buffering humidity fluctuations, fundamentally alleviates the
power degradation of the photovoltaic module caused by
damp heat aging, further extending the service life of the photovoltaic module.