The invention relates to solar cells. More particularly, the invention relates to arrangements and methods to increase the efficiency of solar cells.The methods and arrangements of the invention allow to increase the efficiency of solar cells (11, 12, 13, 14) by trapping photons into the photovoltaic system by thermodynamic shielding based on at least one of the following: conductive shielding, radiative shielding (20, 21, 22, 400, 410, 411) and / or convective shielding.The best mode of the invention is considered to be a tandem solar cell of Si (11) and InSb (12) enclosed in a vacuum container (200) to minimise convective heat losses.Incident sunlight is focused by a lens (320) to a diverging element (310) that disperses the sunlight into the vacuum container (200) and on to the Si (11) layer that is facing the incident side of sunlight. The vacuum container has reflective foil (400, 410, 411) on the inside to reflect retransmitted photons and thereby minimise radiative losses. InSb layer (12) is behind the Si layer (11). The semiconductors are suspended with metal wires, minimising conductive heat losses, which may include the electrical contacts to the load (500) or the DC inverter.